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Chronic tubulointerstitial nephritis - Diagnosis
Medical expert of the article
Last reviewed: 06.07.2025
Diagnosis of chronic tubulointerstitial nephritis is very difficult. In analgesic nephropathy, even at the preclinical stage, Zimnitsky's test reveals a depression of the relative density of urine in most patients. Moderate urinary syndrome (microhematuria, moderate proteinuria) is characteristic. A significant increase in protein excretion with urine indicates the development of severe glomerular damage (most often focal segmental glomerulosclerosis), heralding the development of terminal renal failure. The addition of macrohematuria is a sign of developing necrosis of the renal papillae; if it persists, it is necessary to exclude uroepithelial carcinoma, the risk of which is very high in analgesic nephropathy, especially in smokers. Aseptic ("sterile") leukocyturia is characteristic of analgesic nephropathy.
In chronic tubulointerstitial nephritis caused by lithium preparations, an increase in serum creatinine concentrations is observed, usually moderate. Urinary syndrome and arterial hypertension are rare.
In nephropathy caused by Chinese herbs, proteinuria is detected, usually not exceeding 1.5 g/day.
Patients with chronic tubulointerstitial nephritis caused by lithium are prone to developing acidosis in the presence of predisposing factors (sepsis, hypercatabolic syndromes), despite normal blood pH.
In lead nephropathy, proteinuria values do not exceed 1 g/day, and an increase in the content of tubular proteins is characteristic - beta 2 -microglobulin and retinol-binding protein. The concentration of lead in the blood, as well as protoporphyrin (a marker of heme synthesis disorder) in erythrocytes is determined. To confirm the diagnosis of chronic intoxication with small doses of lead, a lead mobilization test with ethylenediaminetetraacetic acid (EDTA) is used: 1 g of EDTA is administered intramuscularly twice at intervals of 8-12 hours, then the lead content in a daily portion of urine is determined. If the daily excretion of lead exceeds 600 mcg, chronic intoxication with small doses is diagnosed.
Signs of chronic cadmium tubulointerstitial nephritis:
- tubular proteinuria (increased excretion of beta 2 -microglobulin);
- glucosuria;
- aminoaciduria;
- hypercalciuria;
- hyperphosphaturia.
In radiation nephropathy, proteinuria is rarely diagnosed, but cases of significant increases in urinary protein excretion decades after exposure to ionizing radiation have been described.
Sarcoidosis is characterized by hypercalcemia, hypercalciuria, “sterile” leukocyturia, and slight proteinuria.
[ Instrumental diagnostics of chronic tubulointerstitial nephritis
Chronic drug-induced tubulointerstitial nephritis
Histological examination of renal tissue in NSAID nephropathy reveals features similar to minimal change nephropathy; loss of most stalks is observed in podocytes.
Ultrasound examination reveals a decrease in the size of the kidneys and unevenness of their contours. Calcification of the renal papillae is detected with greater reliability by CT, which does not require the introduction of contrast and is currently considered as the standard visualization method for diagnosing analgesic kidney damage. Renal biopsy is inappropriate.
Additional arguments in favor of the diagnosis of analgesic nephropathy are obtained during cystoscopy: characteristic pigmentation of the bladder triangle is observed. Microangiopathy is detected during biopsy of this area of the bladder mucosa.
The diagnosis of tubulointerstitial nephritis when taking Chinese herbs is confirmed by biopsy: the distinctive feature of the morphological picture is the severity of tubulointerstitial fibrosis and tubular atrophy, which developed in a relatively short time from the start of taking Chinese herbs. Cellular atypia is often observed during biopsy of the kidneys and urethral mucosa.
Chronic tubulointerstitial nephritis due to environmental factors
Morphological examination of renal tissue reveals relatively specific signs - edema and vacuolization of epithelial cells of the distal tubules and collecting ducts; during the PAS reaction, glycogen accumulation is noted in them. Glycogen granules in these cells appear within a short time from the start of taking lithium-containing drugs and, as a rule, disappear when they are discontinued. Tubulointerstitial fibrosis of varying severity is also observed. As the disease progresses, the formation of tubular microcysts is characteristic. Biopsy often reveals nephropathy with minimal changes, less often - focal segmental glomerulosclerosis.
In chronic lead intoxication, the kidneys are symmetrically reduced in size; no specific morphological signs of damage have been described.
Chronic tubulointerstitial nephritis in systemic diseases
Morphological signs of sarcoidosis are macrophage infiltration of the renal tubulointerstitium with the formation of typical sarcoid granulomas. Involvement of the glomeruli is not typical.